Technical Field
This application relates to a vascular filter and more particularly to a method of inserting a vein filter into the vessel.
Background of Related Art
Passage of blood clots to the lungs is known as pulmonary embolism. These clots typically originate in the veins of the lower limbs and can migrate through the vascular system to the lungs where they can obstruct blood flow and therefore interfere with oxygenation of the blood. Pulmonary embolisms can also cause shock and even death.
In some instances, blood thinning medication, e.g. anticoagulants such as Heparin, or sodium warfarin can be given to the patient. These medications, however, have limited use since they may not be able to be administered to patients after surgery or stroke or given to patients with high risk of internal bleeding. Also, this medication approach is not always effective in preventing recurring blood clots.
To avoid invasive surgery, less invasive surgical techniques involving placement of a mechanical barrier in the inferior vena cava have been developed. These barriers are in the form of filters and are typically inserted through either the femoral vein in the patient's leg or the right jugular vein in the patient's neck or arm under local anesthesia. The filters are then advanced intravascularly to the inferior vena cava where they are expanded to block migration of the blood clots from the lower portion of the body to the heart and lungs.
These prior filters take various forms. One type of filter is composed of coiled wires such as disclosed in U.S. Pat. Nos. 5,893,869 and 6,059,825. Another type of filter consists of legs with free ends having anchors for embedding in the vessel wall to hold the filter. These filters are disclosed, for example, in U.S. Pat. Nos. 4,688,553, 4,781,173, 4,832,055, and 5,059,205, 5,984,947 and 6,007,558. Another type of filter is disclosed in U.S. Pat. No. 6,214,025 consisting of wires twisted together to form a cylindrical anchoring portion conforming to the inner vessel wall surface to exert a radial force and a conical filtering portion.
Co-pending commonly assigned U.S. application Ser. No. 10/899,429 (the “'429 application”), the entire contents of which is incorporated herein by reference, discloses other forms of vein filters. These filters can be permanently implanted or removed minimally invasively, e.g. intravascularly.
The methods of placement of the filter described in the '429 are effective. However, in certain patients, the vena cava is not straight, but is curved and/or more tortuous. Although the filters of the '429 application can be placed effectively in such vena cava, it would be advantageous to provide a delivery method and apparatus to even better accommodate these curved anatomies.
Additionally, the better centered the filter, the easier the subsequent removal of the filter. This is due to the fact that if the caudal end (the proximal retrieval end) of the filter is against the vessel wall when placed, access to the retrieval end could be difficult. Also, additional tissue ingrowth could occur over the proximal end which could increase the difficulty of removal. Therefore, it would be advantageous to provide a filter delivery system which could improve centered delivery of the filter.